IR Transitions Research Articles

Photoexcitation of oxazine 170 dye in aqueous solution: TD-DFT study.

The vibronic absorption spectra of OX170 dye in an aqueous solution using 40 hybrid functionals, the 6-31 + + G(d,p) basis set, and the SMD solvent model were calculated. It turned out that the long-range corrected ωB97XD functional provided the best agreement with the experiment in the positions of the main maximum and the short-wavelength shoulder. Calculations showed that this shoulder is vibronic and is not caused by a separate electronic transition. At the same time, the shoulder intensity in the calculated spectrum turned out to be lower than in the experimental one. Various parameters of the OX170 cation in the ground and excited states (IR spectra, atomic charges, dipole moments, and transition moment) were calculated. Maps of the distribution of electron density and electrostatic potential have been built. The influence of four strong hydrogen bonds of the dye with water molecules on the absorption spectrum was analyzed. It was shown that these bonds are strengthened upon OX170 excitation. It was found that explicit assignment of water molecules strongly bound to the dye leads to a redshift of the calculated spectrum by ≈15nm as a whole, and worsened its shape. Photoexcitation of the dye leads to a noticeable polarization of only one of the four considered water molecules (associated with the endocyclic nitrogen atom in the central ring of the chromophore, the electron density on which increases the most).

Community Resilience in Belarus and the EU response

Community Resilience in Belarus and the EU response

Visible light-catalyzed fluoroalkylation reactions of free aniline derivatives.

The electron-rich nature of aminoaromatic compounds and the electrophilic character of fluoroalkyl RF radicals allow for a special match in substitution reactions. We herein present visible light photocatalyzed fluoroalkylation reactions of aniline derivatives, with a study of the reaction mechanisms. The examples evaluated make use of different photocatalysts, such as polypyridyl complexes of Ir or Ru transition metals, organic dyes such as Rose Bengal, phthalocyanine-metal organocatalysts, or visible-light activated complexes. Different visible light sources that span from the blue region of the electromagnetic spectrum to low power red light irradiation sources deliver the excited photocatalysts that ensue into the production of fluoroalkyl RF radicals. In turn, many sources of RF radicals can be employed, such as fluoroalkyl halides, Togni's reagents, Umemoto's reagent, etc. All these protocol variants demonstrate the expansion of the methodology and the versatility of photocatalytic techniques applied to a special family of organic compounds such as aminoaromatic substrates, which has been studied by different groups. Contributions from our own laboratory will be given.

Electrochemically deposited iridium-oxide: Estimation of intrinsic activity and stability in oxygen evolution in acid solution

Hydrated iridium oxyhydroxide (IrOx) films were electrochemically deposited from an alkaline oxalic solution at constant anodic potentials and by applying a potential cycling protocol, in both cases with variation of the electrodeposition time. From UV–vis spetroscopy of the solution for the deposition and their characterization it was concluded that a mixture of Ir(III)/Ir(IV) monomers participates in the deposition of IrOx film. X-ray photoelectron spectroscopy (XPS) of IrOx films indicated that both types of films contained hydrated Ir(IV) hydroxide as the dominant species, but in the film deposited by potential cycling the presence of the additional Ir(III) species was evident. The scanning electon microscopy (SEM) analysis of the surface morphology revealed that films deposited by potential cycling were more uniform than the films deposited at a constant potential. The amount of electrochemically active Ir-species on the surface of deposited IrOx films was estimated from the voltammetric charge of the Ir(III)/Ir(IV) transition. Depending on the film electrodeposition parameters, the values between 15 and 1080 nmol cm−2 were obtained. The electrochemically active surface area (ECSA) of IrOx films was calculated from cyclic voltammetry and electrochemical impedance spectroscopy (EIS) measurements and ranged from 3 to 131 cm2 per 1 cm2 of geometric surface area for various films. The activity and stability of IrOx films toward oxygen evolution reaction (OER) was investigated in 0.5 M H2SO4 solution under potentiostatic conditions. The intrinsic activity, stated as turnover frequency and specific current density normalized per ECSA, showed that the OER activity of IrOx films deposited by potential cycling are up to two and a half times higher than the activity of films deposited at a constant anodic potential. Potentiostatic stability test showed a decrease in OER current over time for both type of the films. Determination of ECSA, the amount of electroactive Ir species, XPS spectrum and SEM imaging after the test indicated that the decrease in OER activity was caused by partial dissolution and delamination of the film as well as by oxidation of highly active hydroxide Ir(III) species.

Identification of Correlation between Cation Disordering and the Anionic Redox Chemistry in Li-Rich Layered Oxides

To satisfy our increasing dependence on the high energy storage electronics, Li-rich layered oxides (Li[LixM1-x]O2, M = Ni, Co, Mn, Ru, Ir, etc) have attracted significant attention as cathode materials for lithium-ion batteries in recent years. This class of cathode materials exhibit promising capacities, up to 300 mAh/g, due to accumulative transition metal and oxygen redox reaction1–5. Additional capacity in this class of Li-rich cathode material is due to the anionic redox which is irreversible or partially reversible oxygen evolution6,7 and reversible O2-/n- redox1,3,4,8. Luo el at.1 demonstrated that the localized electron holes on oxygen coordinated by Mn4+ and Li+ ions is promoted by the relatively more ionic interactions of O-(Mn/Li) than O-(Ni/Co) interactions at the result of the oxygen oxidation. In our previous study2, at least partially reversible oxygen evolution was observed in 0.4Li2MnO3-0.6LiMn0.5Ni0.5O2 by using Rietveld refinement of high resolution powder diffraction patterns. In the case of 4d (Ru) and 5d (Ir) transition metal-based Li-rich cathode materials, reversible anionic redox was confirmed by X-ray photoelectron spectroscopy (XPS)3,4. Even though the participation of oxygen in redox activity in Li2MnO3 results in partial oxygen evolution with irreversible structural changes9, oxygen redox reaction is stabilized by the reversible peroxo-dimers (O2 n-) formation in the Li2MO3-based (M = Ru, Ir) Li-rich cathode materials due to the high covalent metal-oxygen environment in Ru- and Ir-based lithium-rich cathode materials. However, Seo et al.10 identified the structural and chemical origin of the anionic redox activity which preferentially takes place along the Li-O-Li configurations (non-bonding O 2p states) in Li-rich layered oxides and cation-disordered oxides by using ab initio calculations based on DFT. The electrons in Li-O-Li states exist in the higher energy states than those in the other O 2p states owing to their unhybridized O 2p and Li 2s orbitals. Through these significant studies, anionic redox mechanism seems to be well established. In the case of Na2RuO3, extra anionic capacity is enabled in honeycomb-ordered Na2RuO3 due to the ordered intermediate Na1RuO3 phase which can accommodate the frontier orbital reorganization11, meanwhile, transition metal migration into the empty Li sites is closely associated with the anionic redox as a result of the structural disordering in Li1.17Ni0.21Co0.08Mn0.54O2 5 and Li2IrxSn1-xO3 systems12. It is still under debating whether such manifold anionic chemistry will be solved in terms of transition metals (3d, 4d, and 5d) or alkali metals (Li and Na) or bulk and local structure. In addition, the different reaction mechanism is confirmed between multivalent iridium redox (Ir4+/5.5+)12 and cumulative iridium (Ir4+/5+) and oxygen (O2-/n-) redox13 even in the same C2/m space group of Li2IrO3 materials.Herein, redox mechanism of Li2IrO3 was investigated as a model compound for Li-rich cathode material to understand the key structural differences that lead to anionic redox activity through the synchrotron-based analysis. The local environment, not the composition itself in Li-rich materials, is one of the major factors affecting the redox reaction. We demonstrate that the in-plane disordering in the transition metal layer play a critical role in cation migration and anionic redox, and that cation migration also can trigger the anionic redox reactions. These fundamental insights about Li-rich material family are critical for further development of anionic redox-based cathode materials. In-plane ordering in pristine state with the same composition of Li2IrO3 has a major impact on cation migration and reversible anion redox. Based on the experimental data, detailed findings and discussion will be presented in the PRiME 2020.References K. Luo et al., Nat. Chem., 8, 684–691 (2016)S. Muhammad et al., Nano Energy, 21, 172–184 (2016)M. Sathiya et al., Nat. Mater., 12, 827–835 (2013)E. McCalla et al., Science (80-. )., 350, 1516–1521 (2015).W. E. Gent et al., Nat. Commun., 8, 2091 (2017)A. R. Armstrong et al., J. Am. Chem. Soc., 128, 8694–8698 (2006).A. Boulineau, L. Simonin, J. F. Colin, C. Bourbon, and S. Patoux, Nano Lett., 13, 3857–3863 (2013).H. Koga et al., J. Electrochem. Soc., 160, 786–792 (2013).J. R. Croy et al., Chem. Mater., 26, 7091–7098 (2014).D. H. Seo et al., Nat. Chem., 8, 692–697 (2016)B. Mortemard de Boisse et al., Nat. Commun., 7, 11397 (2016)J. Hong et al., Nat. Mater., 18, 256–265 (2019)E. McCalla et al., Science (80-. )., 350, 1516–1521 (2015)

Correlation between Cation Disordering and the Anionic Redox Chemistry in Li-Rich Layered Oxides

To satisfy our increasing dependence on the high energy storage electronics, Li-rich layered oxides (Li[LixM1-x]O2, M = Ni, Co, Mn, Ru, Ir, etc) have attracted significant attention as cathode materials for lithium-ion batteries in recent years. This class of cathode materials exhibit promising capacities, up to 300 mAh/g, due to accumulative transition metal and oxygen redox reaction1–5. Additional capacity in this class of Li-rich cathode material is attributed to the anionic redox which is irreversible or partially reversible oxygen evolution6,7 and reversible O2-/n- redox1,3,4,8. Luo el at.1 demonstrated that the localized electron holes on oxygen coordinated by Mn4+ and Li+ ions is promoted by the relatively more ionic interactions of O-(Mn/Li) than O-(Ni/Co) interactions at the result of the oxygen oxidation. In our previous study2, at least partially reversible oxygen evolution was observed in 0.4Li2MnO3-0.6LiMn0.5Ni0.5O2 by using Reitveld refinement of high resolution powder diffraction patterns. In the case of 4d (Ru) and 5d (Ir) transition metal-based Li-rich cathode materials, reversible anionic redox was confirmed by X-ray photoelectron spectroscopy (XPS)3,4. Even though the participation of oxygen in redox activity in Li2MnO3 results in partial oxygen evolution with irreversible structural changes9, oxygen redox reaction is stabilized by the reversible peroxo-dimers (O2 n-) formation in the Li2MO3-based (M = Ru, Ir) Li-rich cathode materials due to the high covalent metal-oxygen environment in Ru- and Ir-based lithium-rich cathode materials. However, Seo et al.10 identified the structural and chemical origin of the anionic redox activity which preferentially takes place along the Li-O-Li configurations (non-bonding O 2p states) in Li-rich layered oxides and cation-disordered oxides by using ab initio calculations based on DFT. The electrons in Li-O-Li states are higher energy than those in the other O 2p states owing to their unhybridized O 2p and Li 2s orbitals without taking into account the covalency between the transition metal and oxygen. Through the significant research efforts, anionic redox mechanism seems to be well established. In the case of Na2RuO3, extra anionic capacity is enabled in honeycomb-ordered Na2RuO3 due to the ordered intermediate Na1RuO3 phase which can accommodate the frontier orbital reorganization11, meanwhile, transition metal migration into the empty Li sites is closely associated with the anionic redox as a result of the structural disordering in Li1.17Ni0.21Co0.08Mn0.54O2 5 and Li2IrxSn1-xO3 systems12. It is still under debating whether such manifold anionic chemistry will be solved in terms of transition metals (3d, 4d, and 5d) or alkali metals (Li and Na) or bulk and local structure. In addition, the different reaction mechanism is confirmed between multivalent iridium redox (Ir4+/5.5+)12 and cumulative iridium (Ir4+/5+) and oxygen (O2-/n-) redox13 even in the same C2/m space group of Li2IrO3 materials.Herein, redox mechanism of Li2IrO3 was investigated as a model compound for Li-rich cathode material to understand the key structural differences that lead to anionic redox activity through the synchrotron-based analysis. The local environment, not the composition itself in Li-rich materials, is one of the major factors affecting the redox reaction. We demonstrate that the in-plane disordering in the transition metal layer play a critical role in cation migration and anionic redox, and that cation migration also can trigger the anionic redox reactions. These fundamental insights about Li-rich material family are critical for further development of anionic redox-based cathode materials. In-plane ordering in pristine state with the same composition of Li2IrO3 has a major impact on cation migration and reversible anion redox. Based on the experimental data, detailed findings and discussion will be presented in the 237th ECS meeting.

Improved ground state and [formula omitted] = 1 state rovibrational constants of formaldoxime (CH2NOH)

The high-resolution Fourier transform infrared (FTIR) spectrum of the ν12 band of formaldoxime (CH2NOH) was recorded at the Australian Synchrotron with an unapodized resolution of 0.0018 cm−1 in the 320–460 cm−1 region. A total of 1895 infrared transitions were fitted using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.000156 cm−1. From this rovibrational analysis, the ν12 = 1 state rotational constants (A and C) and five quartic terms (ΔJ, ΔJK, ΔK, δJ, δK) were improved from previous work and three sextic terms (ΦJK, ΦKJ, ΦK) were derived for the first time. The band center of the ν12 band of CH2NOH was found to be 397.685235(23) cm−1. All five quartic centrifugal distortion terms of the ground state were also improved with higher accuracy. The ground state ΦJK, ΦKJ, ΦK were obtained for the first time through the fitting of 1501 ground state combination differences (GSCDs) derived from the IR transitions of the ν12 and ν10 bands, together with 23 previously reported microwave frequencies. The rms deviation of this GSCD fit was 0.000687 cm−1. Additionally, rotational constants and higher order centrifugal distortion terms of the ground and v12 = 1 states were computed from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVTZ basis set, for comparison with the experimental results. The calculated and experimental rovibrational constants of CH2NOH for both ground and v12 = 1 states were in good agreement.

Hyperfine measurement of the 6P1/2 state in 87Rb using double resonance on blue and IR transition

In this paper, we present the spectroscopy of the 6P1/2 state in 87Rb using a double-resonance technique at 780 nm and 421 nm. The double-resonance technique is implemented using electromagnetically induced transparency (EIT) and optical pumping methods. Using these spectroscopy methods, we have measured the hyperfine splitting of the 6P1/2 state with precision of <400 kHz, which agrees well with other spectroscopy methods such as electrical discharge and saturated absorption spectroscopy at 421 nm.

Interaction of intermediates with transition metal surfaces in the dehydrogenation of ethanol to ethyl acetate: A theoretical investigation

By employing a combined approach of the unity bond index–quadratic exponential potential method and density functional theory within the generalized gradient approximation, we have studied the interaction of intermediates in the ethanol dehydrogenation process to ethyl acetate on Cu, Ag, Ni, Pd, Pt, Co, Au and Ir(111) transition metal surfaces. Binding energies and geometries were optimized for the main intermediates of this process. Electronic structures were computed for some intermediates/transition metal systems. We also calculated the activation energies for the elementary steps of the reactions. The results show that amid the studied surfaces, Cu(111) stabilizes ethoxy and acetyl species, preventing their dissociation. Inducing the η2 binding mode of acetaldehyde by alloying Cu with Ni, Co, Pd, Pt or Ir can enhance the catalytic proprieties of the Cu(111) clean surface.

Synthesis, Physicochemical and Thermal Analyses of Ru(III), Pt(IV), and Ir(III) Complexes with NO Bidentate Schiff Base Ligand

The chemical reaction of the 2-[(2,3-dihydroxybenzylidene)amino]benzoic acid (H3L2) Schiff base ligand with Ru(III), Pt(IV) and Ir(III) transition metal ions form the complexes of formula, [Ru(L)(Cl)2(NH3)2(NH4)2] · 2H2O (1), [Pt(L)(Cl)3(NH3)(NH4)2] · H2O (2), and [Ir(L)(Cl)2(NH3)2(NH4)2](3), where L is deprotonated ligand at pH 8–9. The carboxylic acid group is deprotonated and forms ammonium carboxylates at alkaline media. The infrared spectra of the complexes show that Schiff base ligand is present as a NO bidentate chelate through –N atom of azomethine and –O atom of OH phenolic groups. These complexes are of non-electrolyte nature. The electronic spectra and magnetic moments data suggest the coordination number. Thermo gravimetric studies show that ruthenium(III) and platinum(IV) complexes containing hydrated water molecules outside the coordination sphere that are presence on their thermal decomposition in the temperature range 50–100°C. Solid powder diffraction XRD patterns of complexes show isomorphism confirming their similar formulation. Scanning electron microscopy (SEM) micrographs of the complexes samples confirm the surface homogeneity. In the transmission electron microscopy (TEM) pictures these complexes are present as a dark spots with particle size of 50 nm.

Improved ground state and [formula omitted] = 1 state rovibrational constants of 13C2D4

The rovibrational spectrum of the ν12 band of isotopologue ethylene (13C2D4) was recorded using the Fourier transform infrared (FTIR) spectrometer with an unapodized resolution of 0.0019 cm−1 in the 1000–1140 cm−1 region. From the analysis of this A-type band, the v12 = 1 state rovibrational constants up to four quartic terms (ΔJ, ΔK, δJ, δK) were improved from previous work and a sextic term was derived for the first time. A total of 2403 infrared transitions were fitted using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.00026 cm−1. The band centre of the ν12 band of 13C2D4 was found to be 1069.969827(13) cm−1. The ground state rotational constants (B, and C) and the centrifugal distortion constants (ΔJ, δJ, δK) were improved with higher accuracy while a sextic term was obtained for the first time through the fitting of 1209 ground state combination differences (GSCDs) derived from the IR transitions of the ν12 band, together with 504 previously reported GSCDs of the ν9 band of 13C2D4. The root-mean-square (rms) deviation value of this fit was 0.00027 cm−1. The uncertainty of the measured infrared lines was estimated to be ±0.0003 cm−1. Additionally, equilibrium state rovibrational constants up to five quartic terms, and rotational constants of the ground and v12 = 1 state were derived from theoretical anharmonic calculations at two different levels of theory, B3LYP and MP2 with the cc-pVQZ basis set, for comparison with the experimental results. These calculated ground state rotational constants of 13C2D4 agreed well within 0.60% of those determined from the GSCD fit in this work. Rotational constants (A, B, and C) of the v12 = 1 state of 13C2D4 were also calculated using B3LYP/cc-pVQZ and MP2/cc-pVQZ levels with an agreement of 0.56% or less to those derived experimentally.

The analysis of HF molecule by means of infrared transitions in H + F2 collinear scattering on two different potential energy surfaces

In this study, infrared vibrational modes and intensities are calculated for F2 + H → HF + F reaction according to distance between F and H atoms by using DFT-B3LYP/6-311++G (d, p) level of theory. Also for the relevant reaction, the vibrational energy eigenvalues of the nascent H-F molecule at specific locations of the separated fluorine atom are obtained using the Schrödinger wave equation on the most realistic potential energy surface for this reaction. Since the main aim of the work is to analysis nascent molecular structure by the help of IR transitions, in the light of these two studies indicated above, the most appropriate vibration quantum states supporting the relevant IR transitions are determined and are verified by comparison with experimental results for some transitions that are available in the literature. Moreover, the transition state regions relating to both the reaction and the nascent HF molecule are detected by means of these.

Infrared spectroscopy of jet-cooled HCCl singlet chlorocarbene diradical: CH stretching and vibrational coupling dynamics.

Quantum shot noise limited laser absorption methods are used to obtain first high-resolution infrared rovibrational spectra of jet cooled chlorocarbene (HCCl) diradical in a supersonic slit-jet discharge expansion spectrometer. The rotationally resolved absorption spectra of the C-H stretch ν1 fundamental are analyzed in the framework of a Watson non-rigid asymmetric rotor Hamiltonian model. Further analysis of the mid-infrared data reveals the additional presence of what has nominally been assigned as the combination band with one quantum of the H-C-Cl bend (ν2) and two quanta of the C-Cl stretch (2ν3). Rovibrational constants are obtained from least squares fits for each of the four excited vibrational states built on the ν1 fundamental and the combination mode for each 35Cl and 37Cl atom isotopologue. The four bands occur within a narrow spectral window, requiring detailed comparison of multiple spectral properties (e.g., rotational constant dependence on vibrational excitation, band types/transition dipole moment alignment in the body-fixed frame, etc.) to aid in the vibrational assignment. Indeed, the IR transition intensities arise from strong anharmonic mixing between the "bright" ν1 C-H stretch and "dark" H-C-Cl bend/C-Cl stretch combination modes, resulting in nearly equal amplitudes for the zeroth order and harmonic states. Finally, to aid the spectral search for HCCl in the interstellar medium, ground state two-line combination differences are combined with previous laser-induced fluorescence results to predict precision microwave transitions for HC35Cl and HC37Cl.

DFT Study on the Mechanism of Hydrogen Storage Based on the Formate-Bicarbonate Equilibrium Catalyzed by an Ir-NHC Complex: An Elusive Intramolecular C-H Activation.

A novel iridium based, water-soluble phosphine-NHC (N-heterocyclic carbene) complex, Na2[Ir( emim)(η4-COD)( mtppts)] was previously developed in our research group. It was shown that it is a very effective catalyst for the reversible storage of hydrogen based on the formate-bicarbonate equilibrium. In this paper, we present a DFT investigation on the noninnocent behavior of the NHC ligand toward C-H activation of the N-ethyl side chain and its possible role in the hydrogen storage mechanism. After preliminary investigations, using both computations and NMR measurements, we conclude that the COD ligand leaves the precatalyst irreversibly and the C-H activation takes place on a monophosphine complex. Two main pathways are considered in which the active Ir(III) complexes are generated differently: One is the cyclometalation path involving the ethyl side chain, the other is the oxidative addition step of a water molecule which has a higher barrier but provide a more stable starting state. We find that though the latter, a catalytic cycle where a hydride is abstracted from formate and gets protonated by solvent molecules gives the lowest calculated energy barrier, +25.8 kcal mol-1. That is, avoiding further redox processes is preferred. There are other pathways involving thermodynamically accessible C-H activated iridacycles but those involve slightly higher overall activation barriers due to the required Ir(I)/Ir(III) transitions. The cycle which involves only iridacycle intermediates offer the lowest energy span (energy difference calculated between only the highest and lowest energy points inside the cycle), however. Together with the experimental results, this implies that C-H activation of the N-ethyl side chain happens off-cycle or the starting solvent addition step of the dominant pathway is blocked kinetically. We also discuss the hydrogen uptake reaction catalyzed by cyclometalated species where the reduction of CO2 is preferred over reversing the first main cycle.

The ν8 band of C2HD3 by high-resolution synchrotron FTIR spectroscopy: Coriolis interactions between the v8 = 1 and v6 = 1 states

The synchrotron Fourier transform infrared (FTIR) spectrum of the ν8 band of ethylene-d3 (C2HD3) was measured at an unapodized resolution of 0.00096cm−1 from 830 to 1010cm−1. Rovibrational constants up to five quartic terms were derived with improved precision for the v8=1 state through the fitting of 1566 unperturbed infrared transitions using the Watson's A-reduced Hamiltonian in the Ir representation with a root-mean-square (rms) deviation of 0.00044cm−1. For the first time, 446 perturbed IR transitions of the ν8 band were fitted together with the 1566 unperturbed infrared transitions to obtain the a- and b-Coriolis resonance parameters from its interaction with the v6=1 state, with an rms deviation of 0.00039cm−1. The IR lines of the ν6 band were too weak for detection. Three rotational constants, a quartic constant and band center of the v6=1 state were also derived for the first time in this work. Ground state rovibrational constants of C2HD3 up to five quartic constants were also derived from a fit of 906 ground state combination differences with an rms deviation of 0.00030cm−1 from infrared transitions of the present analysis. The ground state rotational constants are in close agreement with theoretically calculated values using the cc-pVTZ basis set at CCSD(T), MP2 and B3LYP levels of theory. Alpha constants determined from the rotational constants of the v8=1 state derived from the perturbed IR fit compared favourably with those from anharmonic calculations.

High resolution quantum cascade laser spectroscopy of the simplest Criegee intermediate, CH2OO, between 1273 cm−1 and 1290 cm−1

The region 1273-1290 cm-1 of the ν4 fundamental of the simplest Criegee intermediate, CH2OO, has been measured using a quantum cascade laser transient absorption spectrometer, which offers greater sensitivity and spectral resolution (<0.004 cm-1) than previous works based on thermal light sources. Gas phase CH2OO was generated from the reaction of CH2I + O2 at 298 K and 4 Torr. The analysis of the absorption spectrum has provided precise values for the vibrational frequency and the rotational constants, with fitting errors of a few MHz. The determined ratios of the rotational constants, A'/A″ = 0.9986, B'/B″ = 0.9974, and C'/C″ = 1.0010, and the relative intensities of the a- and b-type transitions, 90:10, are in good agreement with literature values from a theoretical calculation using the MULTIMODE approach, based on a high-level ab initio potential energy surface. The low-K (=Ka) lines can be fitted extremely well, but rotational perturbations by other vibrational modes disrupt the structure for K = 4 and K ≥ 6. Not only the spectral resolution but also the detection sensitivity of CH2OO IR transitions has been greatly improved in this work, allowing for unambiguous monitoring of CH2OO in kinetic studies at low concentrations.

Quantum Critical Higgs

The appearance of the light Higgs boson at the LHC is difficult to explain, particularly in light of naturalness arguments in quantum field theory. However light scalars can appear in condensed matter systems when parameters (like the amount of doping) are tuned to a critical point. At zero temperature these quantum critical points are directly analogous to the finely tuned standard model. In this paper we explore a class of models with a Higgs near a quantum critical point that exhibits non-mean-field behavior. We discuss the parametrization of the effects of a Higgs emerging from such a critical point in terms of form factors, and present two simple realistic scenarios based on either generalized free fields or a 5D dual in AdS space. For both of these models we consider the processes $gg\to ZZ$ and $gg\to hh$, which can be used to gain information about the Higgs scaling dimension and IR transition scale from the experimental data.

Alkali Cation Chelation in Cold β-O-4 Tetralignol Complexes.

We employ cold ion spectroscopy (UV action and IR-UV double resonance) in the gas phase to unravel the qualitative structural elements of G-type alkali metal cationized (X = Li(+), Na(+), K(+)) tetralignol complexes connected by β-O-4 linkages. The conformation-specific spectroscopy reveals a variety of conformers, each containing distinct infrared spectra in the OH stretching region, building on recent studies of the neutral and alkali metal cationized β-O-4 dimers. The alkali metal ion is discovered to bind in penta-coordinate pockets to ether and OH groups involving at least two of the three β-O-4 linkages. Different binding sites are distinguished from one another by the number of M(+)···OH···O interactions present in the binding pocket, leading to characteristic IR transitions appearing below 3550 cm(-1). This interaction is mitigated in the major conformer of the K(+) adduct, demonstrating a clear impact of the size of the charge center on the three-dimensional structure of the tetramer.

Multiwavelength Strontium Vapor Lasers

Based on an analysis of experimental and theoretical works, modern notion on conditions of forming of population density inversion on self-terminating IR transitions of alkali-earth metals is given. It is demonstrated that there is a significant difference in the inversion formation in lasers on self-terminating transitions in the visible and near-IR ranges and lasers on self-terminating transitions of alkali-earth metals lasing IR lines in the mid-IR range. It is shown that in the discharge circuit of lasers on self-terminating metal atom transitions (LSMT) there are processes strengthening the influence of the known mechanism limiting the frequency and energy characteristics (FEC) of radiation caused by the presence of prepulse electron concentration. The mechanism of influence of these processes on FEC of the LSMT and technical methods of their neutralization are considered. The possibility of obtaining average lasing power of ~200 W from one liter volume of the active medium of the strontium vapor laser is demonstrated under conditions of neutralization of these processes.

Femtosecond Excited State Dynamics of Size Selected Neutral Molecular Clusters

The work describes a novel experimental approach to track the relaxation dynamics of an electronically excited distribution of neutral molecular clusters formed in a supersonic expansion, by pump-probe femtosecond ionization. The introduced method overcomes fragmentation issues and makes possible to retrieve the dynamical signature of a particular cluster from each mass channel, by associating it to an IR transition of the targeted structure. We have applied the technique to study the nonadiabatic relaxation of pyrrole homoclusters. The results obtained exciting at 243 nm, near the origin of the bare pyrrole electronic absorption, allow us to identify the dynamical signature of the dimer (Py)2, which exhibits a distinctive lifetime of τ1 ∼ 270 fs, considerably longer than the decays recorded for the monomer and bigger size clusters (Py)n>2. A possible relationship between the measured lifetime and the clusters geometries is tentatively discussed.